Solution process for making isobutylene-diolefin synthetic rubber



A. D. GREEN ETAL July 22, 1958 SOLUTION PROCESS FOR MAKING ISOBUTYLENE-DIOLEFIN SYNTHETIC RUBBER FilglNv. 5, 1954 2 Sheets-Sheet l EQFDQOWLUSRLQO. N e L IL .Q .Q ueou m. .Bunn oiv. W... MW DUMRwUhMMOm.

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Lzwai u2 than?? wm MNSQNSQQQ u Nakuwnw Nol tum owk uw?" 455W 2,844 NG IsoBUTYLENE-DIOLEFIN A. D. GREEN EITALl July 2z, 1958 SOLUTION PROCESS FOR MAKI YNTHETIC RUBBER 2 Sheets-Sheet 2 Filed NOV. 5. 1954 20? GWW Nw SUNU .html L03 QOQQ Qmml SOLUTION PROCESS FOR MAKING ISOBUTYL- ENE-DIOLEFIN SYNTHETIC RUBBER Arthur Donald Green, Westfield, Edward J. Gornowski, Cranford, Harold W. Scheeline, Elizabeth, and Stanley E. Jaros, Plainfield, N. I., assignors to Esso Research and Engineering Company, a corporation of Delaware Application November 5, 1954, Serial No. 466,976 19 Claims. (Cl. 260-8553) This invention relates to apparatus and process for the low temperature polymerization of olenic substances; relates particularly to polymerizatio-n processes utilizing a solvent for the olenic monomers which is also a solvent for the polymer; and relates particularly to apparatus and processes utilizing a solvent together with heat exchangers and flow-steps for the recovery of refrigeration in the solution of finished polymer to cool the solution of unpolymerized monomers for subsequent polymerization. This application is a continuation-in-part of application Serial No. 125,422, tiled November 4, 1949, and now abanboned, entitled Improved Solution Process for Making Isobutylene-Dioletin Synthetic Rubber, inventors Arthur D. Green, Edward J. Gornowski, Harold W. Sche/eline, and Stanley E. J aros.

As is well shown in U. S. Patents Nos. 2,356,127, 2,356,128, and 2,356,129, a very valuable elastomeric polymer which is particularly valuable as a replacement for rubber can be produced by the copolymerization of isobutylene and a multiolen at reduced temperatures, by the application to the oletinic material mixture of a Friedel-Crafts catalyst, and a semi-continuous process has been developed by means of which very large quantities of commercial polymer have been produced. This procedure utilizes a diluent which is mixable with the olefinic monomers, but which is a non-solvent for the polymer. This process produces a slurry of polymer in diluent at low temperature which is discharged into warm water to volatilize out the diluent and unreacted monomers, and produces a slurry of polymer in water from Which the polymer is recovered by a straining and drying operation. This process has proved to be commercially feasible, but it is undesirably expensive because of the loss of refrigeration in the relatively large amount of cold diluent and unreacted olenic monomers discharged into the warm flash tank.

In this process it is essential, in order to remove the polymer from the reactor, that the solid polymer be retained in slurry form during the polymerization. However, the polymer is strongly solvated by any hydrocarbons present in the reactant mixture and to insure the maintenance of the polymer in the form of slurried particles, and to prevent coalescence it is necessary, both to operate the reaction at a very low polymerization temperature to reduce the effect of the solvation, and it is also necessary to maintain the lowest possible monomer concentration as distinguished from polymer content in the reactant mixture as possible, in order to avoid the formation of large masses of coherent polymer which interrupt the circulation, and are too large to be discharged through the overflow.

Also, the molecular weight of the polymer produced is a function, both of the lowness of the temperature, the purity of the reactants, and the concentration of monomers present.

Accordingly, by the use of good purity reactants and a relatively high concentration vof reactants, satisfactory molecular weight can be obtained at temperatures as high as nited States Patent() `2,844,569 Patented Jury 2a, tess 50 C. to 40 C. or even higher, but in the prior process, since the monomer concentration must be kept low to prevent coalesc'ence and destruction of the slurry, the ternperature must also be kept very low in order to obtain the desired molecular Weight. Accordingly, in order to maintain reasonable periods of operation, it has been found necessary to utilize polymerization temperatures ranging from 85 C. to 103 C., and a monomer concentration in the reactant mixture well below 10%.

The amount of refrigeration required for such operation is very expensive, and none of it can be recovered, since the slurry must be discharged immediately into warm water in order to convert the slurry of polymer in diluent, and unsaturates into a slurry in water.

In addition, the process is not truly continuous, since some polymer is deposited in solid form on the interior walls of the reactor, where it interferes with transfer of heat to the refrigerating jacket, and must be cleaned off periodically at intervals ranging from 20 to 150 hours, which cleaning procedure involves a shut-down of the reactors, the use of large quantities of solvent, Warming up to room temperature, and a dicult reactor restarting problem which tends to produce off-grade polymer.

It has been suggested that the copolymer can be prepared from monomers dissolved in a material which is a solvent for both the mono-mer and the finished polymer, but such operation, when carried out along conventional lines, is unsatisfactory, because of the exceedingly high viscosity of polymer solutions, especially at low temperatures; that is, copolymer having a Staudinger molecular weight number between 35,000 and 60,000, which is the desirable range, if dissolved in carbon disulfide to the extent of 10%, is, at the polymerization temperature, too viscous to be pumped, and flows so very slowly as to be almost impossible to handle, and only when the concentration is held below 4% or 5% can the col-d solution be handled in pipes and pumps. Accordingly, the previous continuous processes become even less efficient if the polymer is produced in solution, because of the limitation on the polymerA concentration, since the cold solution to be handled, must be kept below 3%, 4% or 5%, whereas a cold slurry has a low viscosity and can be handled at concentrations as high as 15%, 20% or even 25%.

Also, such high viscosity values cause a very low rate of heat transfer and also poor and dicult catalyst dispersion. 1 According to the present invention, it is now found that a solution of the desired olen monomers in almost any desired proportion can be prepared in a low boiling hydrocarbon, a light naphtha, with a boiling point preferably in the general neighborhood of room temperature, particularly suitable solvents being propane with a boiling point at or near 40 C. or commercial butane with a boiling point at or near 6 C. or pentane with a boiling point just a little above room temperature, or commercial hexane with a boiling point at or near -I-69 C. While the solvents mentioned are entirely satisfactory in certain operations, it may be desirable to maintain a single homogeneous phase during the heat exchange stages. While a solvent such as butane will result in a single homogeneous phase at temperatures below about 15 F. at polymer concentrations of about 5%, two liquid phases Will result in temperatures higher than about 15 F. Thus, if butane is utilized as the solvent two liquid phases will be secured when the butane polymer solution is raised in heat exchange to about F. in contact with the incoming feed. Thus, if it is desirable to maintain a single homogeneous liquid phase the preferred solvents are commercial hexane or heptane or a mixture of these. This mixture of olefns and solvent may be prepared in Whatever concentration is most advantageous from the point of View of obtainable ml lecular weight in terms of vthe purity of reactants and desirable temperature. This Vmaterial 4is then further treated by cooling it (as by countercurrent flow) in a tubular heat exchanger, adding a catalyst solution when the temperature has reached the desired low .value preferably in a second heat exchanger having-,a refrigerant jacket such as boiling liquid ethylene as A.the lcooling medium. n

Alternatively, liquid ethane or liquid ear-bon .dioigide or liquid sulfur dioxide or other .convenient refrigerant may be used in the cooling jacket. ',The reaction may then be completed ina soakingdrum at'the Vdesiredlow temperature, the 'amount lof polymerization being limited by restriction of the catalyst to an extentsuchthat: the amount of dissolved solid polymer is low enoughto produce a solution which has a low enough viscosity to be readily owable,and thin enough to avoid interference with heat transfer and catalyst dispersion. .This low concentration solution of polymer in ysolvent and unpolymerized monomers is then used-as cooling medium for incoming .monomer solution, bringing the temperature of the product .solution to the boiling point of the solvent (at .whichtemperature the viscosity is greatly reduced), boiling o" a major proportion of the solvent and unpolymerized monomersunder anhydrous conditions to permit either ofdirect condensation and reuse after theaddition of .more oletinic monomer as polymerization material, or theboiled oi material may be fractionated and remixed for -recycling; the residue of dissolved -solid polymer. at solution concentrations of from to 35%, at a relatively elevated temperature, being-then discharged into hot water via a special atomizing -nozzle or other suitable specialmeans for producing water slurries from solutions for volatilization of the remaining diluent and any residual traces ofmonomer, and the production of a slurry of polymer in Watervwhich can be strained, the polymer driedand furtherprocessed as in thevprior art.

Thus, the ,system of the invention provides a mixingand blending mechanism in which isobutylene ofadequate purity is mixed (in major proportion if desired) withea minor proportion, if desired, of a multiolen having from 4 to 14, inclusive, carbon atoms per molecule, andvfrom 3 to 25 volumes of light naphtha having a boiling -point within the range between 40 C. and +69" C. to produce the raw material as .feed for the reaction.

The blending mechanism is connected to a Aseries of heat exchangers invwhich the blended feed is cooled toa temperature close to polymerization temperature by eoun tercurrentfow with a cold solution xof finished polymer. Ihe heat interchangers Qare'then connected in turnto another heat interchanger cooled by boiling liquid ethylene. Two duplicatecoolersare provided, which serve alternately, ,one as cooler for the incoming 1feedthe Kother Y as cooler for circulating partially polymerized material. These two heat interchangers .are provided with valvesystems whichpermit interchanging their respective functionsso that one serves to.cool the partially polymerized circulating mixture .until .itis fouled ,by adherent polymer, while the other. is lbeing .washed-free from adherent polymer, and simultaneously cools. the incoming feed. f

The ethylene jacketed cooling .exchanger which serves to cool the circulating, partly polyrne'riuzedmaterial, is connectedgto a mixing nozzle which is alsoconnected yto adissolver for preparingthe catalyst solution. The.. rnix-y ing nozzle'then is connected to areactionldrum which is equipped witha circulating pumpconnectedimturn to the ethylene jacketed heat exchanger. An ethylenecooled circuit is Lthus provided, includinggthe 'ethylene jackeyted cooler, mixing nozzle, reactor. drum and.,circulating,pump.` An overilow means from thiscircuit is.' thenprovided, with atransfer pump leading to a second reactoridrum in which-the last trace of catalystactivity occurs. This drum thus contains `a dilute solution of finished polymer. The seconddrum is connected to the countercurrent heat exchangers in which. the entering feed is cooled as much possible, while the product SelutQn. isiheafed, as .much

as possible. The outgoing polymer solution is then led to a series of evaporators in which a large portion of `the diluent-solvent and substantially all of the unreacted monomers are boiled off. A-freetionating system and a condensingsystem operating under elevatedpressuresmare also VVappropriately connected to sthe evaporators for the recovery, separation and condensation of the evaporated material. ;'The evaporators are then connected to a flash drum .in .which the last traces of. volatile hydrocarbon materialare driven `-out from theunevaporated polymer solution, and a` slurry Aof, polymerin *water produced.

By this sequence of process steps, andcombination of apparatus, a copolymer is produced at a low temperature in dilute solution,.whereby asuitable .polymer is obtained, with a minimum amount of refrigeration and a minimum of .drying and .separation of monomers and Arecycled solvent.

Also, the systemand .procedure reduces to aV minimum the difficulties otherwise encounteredv from fouling of reactors, thus making it possible to .maintain continuous operation over .prolonged periods of time at 4maximum capacity, withaminimum of .operations .for cleaning and overhauling.

Other objects vand details vof-.the invention will be apparent from the following.descriptionwhen read in connection .withthe accompanying drawing, wherein:

,Fig l isa diagrammatic representation of apparatus suitable forrpolymerization.intnormall butane solution; and Eig 2 is. a diagrammatic representation of asimilar system arranged for polymerization in 4isopentane solution.

Inrthe process of this invention, the primary. rawmaterials are .isobutylene, anda-multioletin having from 4.to,about 14 carbon atoms` per molecule. vThere is also requiredv a diluent which may bel either propane, one or moreof the several isomeric butanes, kone ormore of the several isomeric pentanes, orone or moreof the several isomerichexanes (or. @heptane ,orgoctane i-ftdesired, although for most purposes the boiling .points ,of these materials are undesirably high).

It maybe noted-thatthe list of s substances usable for diluent-is relatively small since the substance must be liquid at the polymerization.temperature, and,must,be solvents for the polymer at-the, polymerization temperature, and in addition mustV be `free from interferencewith the catalystor the reaction. This requirement rules out the lower alcohols which react with the catalyst and are not solvents for the polymer. It likewise rules out the rethers, aldehydes and organic acids, all of whichare non-solvents for the polymer, and most of which tend-tointerfere with the catalyst.

The hydrocarbon solvent materials are normally obtained from the xed gases derived from petroleum cracking operations. Theisobutylene is preferably of relatively. high purity, as .from 9,6% to 99.5% purity, although thepresence of butane, eithery normal or iso, isI immaterial. However, unsaturates suchas traces of propylene, butene- 1 and butene-2 are preferablykepttovas low .values as possible. It isA highly desirable ythat such. unsaturated impurities be kept below 0.5%, and it is highly. desirable that the amount of butene-Z present be keptlbelow 0.1%.

The solvent-,diluent may, as;a bove indicated, consist of propane, butane, pentane, or hexane, or4 occasionally heptane or octane, and it is desirable that this material be as free Vas possible from interfering unsaturates The material preferably consists :of narrow ,cut virginnaphtha in order to avoid as much as possible the `presence of unsaturates generally. The presenceof traces of lower boiling saturates is immaterial, but the presence of heavy en ds is undesirablebecauseof the` diicultynof getting them out from the polymer during the Water slurrying and finishing operation. Since, however, much of the diluent will be recycled, a somewhat careful purifying operation on the recyclestockis usually necessary. v Also,

it is usually better lto avoid mixtures of diluent substances, since the use of mixtures tends to introduce a troublesome separation problem in the handling of recycle material.

The third component ofthe mixture is a multioleiin having from 4 to 14, inclusive, carbon atoms per molecule such as butadiene, isoprene, dimethyl butadiene, myrcene, dimethallyl, Z-methyl 3-nonyl butadiene l-3, or 2methyl 4-pentyl butadiene l-3, or the like.

For the purposes of this invention, any hydrocarbon unsaturate containing 2 or more units of ethylenic unsaturation, without regard to the configuration may be used as the third component.

These raw materials are preferably mixed in appropriate blending equipment. The isobutylene usually is delivered as a liquid at atmospheric temperature under pressures of about 40 lbs. per square inch (depending upon the actual ambient temperature), the solvent-diluent likewise may be delivered as a liquid at room temperature under similar nominal pressures, depending upon the diluent chosen; pentane and hexane being liquid at room temperature and atmospheric pressure. The proportion in which the isobutylene and the multioletin are mixed depends upon the particular copolymer to be made. If the copolymer is to have an iodine number (by the Wije method) below about 50, and isoprene or a higher multiolelin is to be used, the isobutylene will be present in major proportion and the multiolefin in minor proportion. That is, if isoprene is used with the isobutylene is a mixture containing from 1 to about 7% by volume, the copolymer will contain from about 0.3 to about 5 molecular percent of copolymerized isoprene.

With butadiene approximately 30% by weight is required in the feed mixture to produce a copolymer containing 3 to 5 molecular percent of butadiene. This procedure, however, is very easy with the present process, since the presence of excess, unpolymerized monomers does not matter and by simple adjustment of the feed, a suitable proportion of butadiene is readily obtained without interference to the polymerization reaction, as is otherwise unavoidable in the processes of the prior art.

With cyclopentadiene the copolymerization ratio is considerably higher, so much so that cyclopentadiene tends to copolymerize in a proportion greater than that present in the mixture. In this instance also, by adjustment of the proportion of isobutylene present, the desired amount is readily copolymerized into the mixture.

The polymerization is caused to occur by the use of a Friedel-Crafts active metal halide catalyst in liquid form. The preferred catalyst material is a solution of aluminum chloride in methyl chloride and this catalyst is operative with mixtures containing any or all of the above-outlined multi-unsaturates. Nearly as satisfactory is a solution of boron trifluoride in methyl chloride, or in a low-boiling hydrocarbon which conveniently may, if desired, be the same hydrocarbon which is used for solvent diluent.

Alternatively also, aluminum bromide in solution in a convenient hydrocarbon which may be the same as the diluent, may likewise be used, and aluminum bromide shows a satisfactory solubility, not only in methyl or ethyl chloride, but in the lower boiling hydrocarbons. In many operations it is desirable to carry out the operation with an all-hydrocarbon system and to eliminate the use of materials such as methyl or ethyl chloride. Under these conditions it is very desirable to employ as the catalyst aluminum bromide.

Thus, for the catalyst, there is preferably used a Friedel- Crafts active metal halide catalyst in solution in a low freezing non-complex forming solvent. For the active metal halide, any of the materials shown by N. O. Calloway, in his article on the Friedel-Crafts synthesis, printed in the issue of Chemical Reviews, published for the American Chemical Society at Baltimore in 1935, volume XVII, No. 3, the article beginning on page 327, the list being particularly well shown on page 375, may be used.

For the solvent, to be low freezing, it is merely necessary that the freezing point be below 0 C., and it is not necessary that the freezing point be below the polymerization temperature, since the catalyst solution may be added in liquid form at a temperature above the polymerization temperature and it dissolves in the polymerization mixture before any sign of congealing or freezing out occurs.

To be non-complex forming, it is merely necessary that instillation to, or distillation from the solute of the solvent shall result in minor or negligible change in boiling point of the solution from the boiling point of the pure solvent, and that a smooth change in boiling temperature shall occur as the concentration changes, and in generalthat the solute can be recovered unchanged merely by evaporation of the solvent.

The feed mixture of monoolen, multiolelin and solvent-diluent may be prepared in any convenient manner at any convenient temperature and the catalyst solution likewise may be prepared in the usual apparatus at a convenient temperature. These steps need not differ from the steps of the prior art, since they provide merely the raw materials for the polymerization reaction.

Referring to the figures, particularly Fig. 1 (which shows a first embodiment for the production of a copolymer of isobutylene with isoprene, utilizing normal butane as solvent diluent), the feed mixture of isobutylene, multiolen and solvent-diluent is then supplied through a pipe line 1 to a series of heat interchangers 2, 3, 4, 5, and 6 (a series of exchangers is shown for maximum of cooling etiiciency; one exchanger could be used). Since it is extremely desirable that the feed mixture contain the lowest possible amount of moisture, it is frequently desirable that the mixed feed, after partial cooling, be passed .through a calcium chloride dryer 7. This, while highly desirable, is however not an essential portion of the invention (since the feeds and recycle streams are previously well dried by distillation).

From the heat interchange coolers 2, 3, 4, 5, and 6, the blended feed mixture is conveyed through a pipe line 8 to a circulating polymerization system 9. This system desirably consists of at least two ethylene-cooled Chillers 11 and 12, one of which is connected by suitable piping to a position between the primary coolers and the circulating system, while the other is connected through pipes 14, 15 and 16 to a nozzle device 1'7, which in turn is connected through a pipe line 18 to a reactor drum 19. The reactor drum 19 in turn is connected to a circulating pump 21 which is connected through pipes 22 and 23 to the ethylene Chillers 11 and 12. The catalyst nozzle 17, likewise is connected through a pipe line 24 to the supply of catalyst solution. Appropriate pressuring or pumping means are provided between the storage tanks for the blended feed and the pipe 1 and the catalyst storage tank and the pipe 24 to insure a proper flow of raw material and catalyst to the polymerizer system 9, as above pointed out, the piping is so arranged that either of the Chillers 11 and l2 may be'connected between the circulating system, and the primary coolers, while the other is connected in the circulating system 9.

It may be noted that two ethylene coolers 11 and 12 are provided. These are connected in parallel with valve controls to permit the use of either one for cooling the circulating mixture, and the other for final cooling of incoming feed. It may be noted that there tends to be some fouling of surfaces in the system, in spite of polymerization in solution. This is immaterial in the reaction drum 19, since a layer of adherent polymer merely improves the heat insulation of the drum. It is undesirable, however, in the circulating cooler. However, the fresh cold feed of isobutylene, multiolefin, and solvent has a strong dissolving action on any adherent polymer, and accordingly, by passing the cold fresh feed through one cooler in the absence of catalyst, any fouling polymer is readily removed, then when the other cooler has picked up a significant amount of fouling layer, the position of the 7 two are reversed, the clean cooler being used for cooling the circulating polymer solution, and the fouled cooler being used for the final cooling of the fresh feed and simultaneous cleaning from adherent polymer.

A pump member 25 is likewise connected to the c1rculating system 9, preferably to the pipe line 16. The pump 25 serves to provide the necessary pressure for discharge of polymerized solution from the circulating system 9 to the `second side of the heat exchangers 6, 5, 4, 3, and 2. To the discharge outlet of the pump 25 there is connected a drum 26 which provides storage for the dilute polymer solution and permits of completion of the polymerization reaction. The .dilute polymer solution is then led through 4the heat exchangers in reverse llow to the direction of tiow of the fresh feed. By this procedure, the fresh feed enters the circulating. system 9 at a temperature very close to the polymerization temperature, different in fact only -by the amount of temperature gradient through the metal of the heat exchange surfaces, and the dilute polymer solution leaves the last heat exchanger `2 at nearly the temperature of the incoming feed, again different by substantially only the yamount of temperature gradient through the metal heat exchange surfaces.

From the last heat exchanger 2 the dilute Warm polymer solution, under pressure sufficient to maintain liquid condition, is led through a pipe line 27 and through preheater 28 in which the temperature is raised still higher, preferably to or above the boiling point under the applied pressure. From this preheater 28, the dilute polymer solution is conducted to a disengaging drum 29, in which a very substantial portion of diluent and residual unpolymerized unsaturates are vaporized and discharged through a pipe line 31 to ,a fractionating system 32 consisting of a bubbler-plate column still 33. This still serves to recover a major portion of the methyl chloride catalyst solvent when such is used, for the preparation of further quantities of catalyst solution.

The residue or bottoms from the column 33, consisting mainly of hydrocarbon solvent-diluent and unsaturates is then conducted to storage where it can be fortified with additional quantities of lisobutylene and multiolefin and returned as blended feed to the pipe line 1.

Vaporization of solvent and rapid disengagement of volatiles in the drum 29 is effected by a circulating pump 35 which draws warm polymer solution from the bottom of the drum 29 and delivers it through a boiler 36 to the top of the drum 29 where a substantial portion evaporates and the remainder drains to the bottom of the drum. A pump 37 is connected to the bottom of the drum 29 to withdraw a substantial portion of the warm solution and deliver it .to a second disengaging drum 38. The drum 38 is provided with a circulating pump 39 and a boiler or heat exchanger 41, preferably heated by steam. It may be noted that most of the heat of vaporization is provided by steam in the boiler 41, which heats a circulating stream of polymer, disengaging most of the vapor which is to be disengaged. The major portion of the evaporization effect thus is obtained in the boiler 38. This second drum, heater and circulating pump completes the concentration of the polymer solution to the thickest flowable consistency. The disengaged hot vapors from the drum 38 are sent back through a pipe line 42 to the heaters 36 and 28. The thick residual solution from the drum 38 is discharged through a pipe line 43 which leads to a ilash dmm 44. The thick warm polymer solution from the pipe 43 is delivered through a nozzle 4S into a receiving pipe 46, into which there 'is also entered a steam line 47, both being connected to the drum 44. The steam line 47 is connected to a steam jet within the member 46 which serves to break up, atomize and `heat still further the stream of concentrated polymer, and re-' duce the partial pressure of the solvent vapor by the dilution effect.

This nozzle desirably-.is made asl shown in 2U. S. application Serial No. 780,210, now Patent No. 2,607,763, there being provided a jet for the introduction of a stream of polymer which is intermingled with a jet of steam under vconsiderable pressure. The jet of polymer may be delivered into a concentric jet of steam, or the polymer may be delivered through a series of circular-ly positioned jets, surrounded by a series of tangential `jets of steam to yield the maximum turbulence and temperature in the jet structure. This system vaporizes substantially all of the volatile material 'from the polymer solution, and convert-s the polymer into particles which are wetted and carried along by the turbulent current of steam and water circulated to 46.

It may be noted that the stream of hot polymer solution is quite viscous, and in order to obtain a satisfactory, flowable slurry, free from chunks, the stream of polymer solution must be broken up into relatively small drops at a temperature suiciently high to disengage most of the remaining volatiles, and `these particles must be delivered intothe warm Water in the tank 44 before there is an opportunity for them to coalesce. Accordingly, the steam jet through the pipe-47 must be supplemented by a water jet through the `pipe 40, preferably delivered in the form oftangentialjets of Water. This water preferably is obtained from the drum 44, being recirculated by a pump (not shown). Thus the water delivered through the pipes 40 .or 350, or both, may be fresh water or may be a circulated stream of warm water and slurried polymer.

The vdrum 44 is about half filled with a slurry of polymer in water. It receives the freshly formed slurry from pipe V46. Drum I44 also serves to disengage vapors of solvent and unpolymerized unsaturates from the water and polymer. The vaporized material from the ash drum 44 is delivered to'a condenser 48 to condense the residual diluent and residual monomers. The vpressure in drum 44 is maintained suthciently high to permit condensation of this stream with `cooling water.

It may be noted that most of the process steps here disclosed may be conducted under considerable pressures. In the iirst Yheat interchangers, the vfinal coolers and the polymerizing system, the pressures may be any convenient value, since the necessary low temperatures for satisfactory polymerization bring the boiling points below those at atmospheric pressure. However, in the several heaters to Which'the polymer solution is delivered by line 27, substantial pressures are desirable. These pressures may be produced by the pump 25, and may be such that the vapors disengaged in the tank 29 may leave the tank under suiiciently high pressure' to insure condensation in the column 33 at convenient temperatures, which may be close to room temperature, or to available cooling water temperatures. In consequence', the distilled methyl chloride may be readily condensed to a liquid for the making of catalyst solution, and the recycle material may leave as a liquid, ready for Whatever further processing is necessary. Similarly, the second stream of recycle material taken from the heat exchanger 28 may likewise be under suiicient pressure to be a liquid at some convenient temperature which also may be near to room temperature, or cooling water temperature.

Also, by the maintenance of moderately elevated pressures, the vapor discharged from the top of the flash drum 44 may be under such pressure that cooling water in the heat exchanger 48 will condense substantially all of the vapors, permitting ready separation of water under pressure through the pipe 61, and liquid hydrocarbon material through the pipe 52 to the separating tower 5S. By the use of these pressures, it becomes possible to avoid the use of compressors for compressing and liquefying gas of any sort, and all of the pressures are readily obtained merely by the pumping of liquids, and in `addition, a minimum amount of refrigeration is required,-

9. thereby greatly reducing the amount of refrigerant to be compressed and cooled.

It may be noted that if a hydrocarbon solvent-diluent is used, having a boiling point substantially above the boiling points of the catalyst solvent and isobutylene, these two latter components practically all are evaporated in the drums 29 and 38, and recovered for recycle under anhydrous conditions in the fractionating tower system 32, and practically only the solvent-diluent and multiolefin are volatilized in the drum 44. Under these circumstances, only a moderate cooling is needed in the condenser 48, and a mixture of water and solvent leaves the condenser 48, and enters the collecting tank 49. In this tank the water settles to the bottom and is drained out through a drain pipe 51, and the solvent is drawn off from the upper layer through a pipe 52, conducted to a pump 53 and thence delivered through a pipe 54 to a fractionating column 55.

In the tower 55 traces of water dissolved in the solvent are removed by distillation and discarded overhead through the pipe 56. The bottoms from the tower 55 then consists of primarily C4 and C5 hydrocarbons, substantially free from moisture. The bottoms are delivered through a pipe 57 to a second fractionating tower 58 in which all of the butenes and a little n-butane are taken overhead through a pipe 59 to the methyl chloride recovery tower 61, from which the overhead consists of methyl chloride not evaporated in drums 29 and 38 and some C4 material, which is returned to the feedblending tank for recycle to the pipe 1. The bottoms from the tower 61 are taken through a pipe 63 to another tower 64, the overhead from which is a C4 stream rich in butene l, a reaction poison, which is purged through a discharge pipe 65, and the bottoms, consisting of relatively pure butane and isobutylene, are discharged through a pipe 66 to the feed mixing system for recycle. The bottoms from the fractionating tower 58, containing substantially all of the isoprene and the bulk of the nbutanefed to tower 58, are led through a pipe 67 to a fractionating tower 68, where high boiling impurities are purged as bottoms through a pipe 71 and discarded while the purified isoprene and n-butane is taken off overhead through pipe 69 to the feed blending tank for recycle to pipe 1.

The steam jet in the structure 46 which drives otf the last of the volatiles from the polymer also wets the polymer, and breaks it up into relatively small particles, which are slurried in the drum 44. These particles are significantly lighter than water, and tend to cream on the water. However, a very vigorous stirring and circulation is maintained in the drum 44 by a stirrer (not shown) to maintain a practically uniform slurry of polymer in water. This slurry of polymer in water is delivered through a pipe '72 to a second drum 7.3, in which further traces of unsaturates are disengaged and discharged through a take-off pipe 74. Drum 73, likewise, is equipped with an eicient stirrer to maintain the slurry, and a steady stream of slurry in water is taken through pipe 75 to the iinishing system. This system is not shown, since it is merely the standard finishing system of the prior art, consisting of a strainer, which may be a rotary vacuum type filter, or may be a vibrating screen'separator, or other type of strainer, or tilter as desired. It may be noted that a filter press, while usable, is less efficient, because of the necessity for opening and closing the press, and it is preferable that a continuous iilter be used. The loose, moist, solid polymer is then discharged to a convenient dryer, preferably by way of a conveyor belt. The dryer may take the form of any convenient drying system, but preferably is a link belt type of hot air tunnel dryer, in which the belt is treated with an anti-tack agent, such as a :fine spray of castor oil, the polymer dropped onto the belt at the entrance end, and conveyed through the hot air tunnel dryer to the exit end. The necessary temperature for eiective drying is close to the softening temperature of the polymer, and accordingly, the material at the exit end tends to be more or less adherent and coalesced. The emerging sheet of sintered solid polymer may then be cut into strips across the length of the sheet, dropped onto a conveyor and carried to an extruder where the necessary working brings the polymer to a temperature well above the boiling point of water, and into a plastic condition, where the last traces of water are readily removed.,

Standard practice delivers the polymer from the strainer with from 20% to 80% of moisture. The tunnel drying oven reduces this amount of moisture below 1% in the emerging sheet of polymer. In some instances the water content may be less than 0.1%, and sufficiently low for subsequent processing needs. However, such low values are obtainable only under advantageous conditions, and it is usually desirable to use the extruder in addition, which brings the water content below 0.5%, which is satisfactory for all known commercial uses. From the extruder, the polymer is delivered via a belt conveyor to a double roll mill on which a rolling bank of polymer is formed, from which a strip of practically water and air-free polymer is taken. This strip may be carried over a cooling belt, cut into squares and packaged in appropriate cartons, which are preferably coated on the inside with anti-tack agent to prevent difliculty in unpacking the material from the package preparatory to milling, compounding and fabrication into the desired finished structure.

In the operation of this embodiment of the system, the raw feed is prepared as above described, preferably consisting of approximately to 98% of isobutylene with from 2 to 5% of isoprene. This mixture is then diluted with the solVent-diluent preferably consisting of butane, free from unsaturates, as received from the plant purifying system. As above pointed out, it is immaterial whether this material is normal or isobutane, but it is desirable that it contain the smallest possible quantity of butene-1 or butene-2.

Simultaneously, the catalyst solution is prepared, preferably consisting of aluminum chloride in solution in methyl chloride in a concentration of approximately 0.1 to 2.0% (although in some instances, still higher concentrations, up to saturation, may be used). In starting operation, of course, there is no cold feed in the heat exchangers 3, 4, 5 and 6, and the feed must be passed along to the ethylene coolers 11 and 12, in which the entire cooling load is temporarily carried.

When the circulating system 9 is filled with feed and the temperature brought down to the desired point, which is preferably between 95 C. and 103 C., the flow of catalyst through the pipe 24 and the mixing nozzle 17 is started. Polymerization begins as soon as the catalyst concentration reaches the critical minimum or threshold value, and an overflow of cold polymer solution takes place through the pump 25, the drum 26 and the heaty exchangers 6, 5, 4, 3, and 2. This countercurrent cooling of the incoming feed by the outgoing polymer solution effects a very great saving in refrigeration; between 45% and 55% of the refrigeration otherwise needed being saved; the refrigeration needed being only suilicient to take care of the heat of reaction in the circulating reaction system 9 (and the usual heat leakage losses).

As above indicated, the preferred polymerization ternperature is that obtained by liquid ethylene, since it permits of the use of isobutylene which has not been highly purified. However, if a little higher purity of isobutylene and isoprene are used, or a little higher monomer concentration is used, liquid ethane may be used for the final refrigerant, yielding a temperature within the range between 88 C. and about 80 C. With still higher purity reactants, or higher concentration, liquid carbon dioxide may be used, yielding a temperature somewhat about 78 to about 680 C., and,

L1 ifmaximum purity materials `and maximum concentration are used, a satisfactory polymer can be made with liquid propane as a refrigerant, operating at temperatures between 4about 40 C. and about 35 C.

It may be noted that most of the polymerization .reac-` tion occurs yin the drum y19, and occurs under conditions where there is -ample solvent to maintain solution of the polymer as formed. Nonetheless, in some instances, small vquantities of polymer adhere to the inside rof -the drum 19. This, however, is immaterial, since 'there is no heat exchange through the walls of the drum 19, and thecoating of polymer will not interfere with the process and can be removed at infrequent intervals.

It vmay be noted also that the amount y-of catalyst solution required for the copolymerization vof a given amount of mixed oleflns varies very greatly with the purity and `physical vcondition of the feed and catalyst solvent, and may range lfrom as much as one ypound of aluminum chloride per 300 `pounds of copolymer produced to one pound vof aluminumchloride per 2500 pounds of polymer produced. The reason for this variation is still not definitely known, but it is suspected that it is due to the presence of trace-impurities, such as HC1, moisture, and many other substances which may be present in small amounts, in spite of the most careful purifying treatment of the components of the blended feed and catalyst solvent. As above pointed out, the polymer solution leaves the last heat exchanger at a temperature close to the Atemperature of the entering blended feed which may be anywhere between room temperature and the boiling point of the mixed feed.

Thedilute polymer solution, warmed up nearly to its boiling point, is then carried through a preheater to -a disengaging drum, Where a large portion, which may be as much as 3A to 'Vs of the diluent and unsaturated residual monomers, are boiled out.

:It may be noted that this evaporation occurs under anhydrous conditions and that the more volatile catalyst solvent component is selectively vaporized from ythe lirst effect. of the evaporator so Athat -a pure catalyst solvent can be prepared with a minimum of further purification and no dehydration step is necessary. Furthermore, a large bulk of the C4 material is obtained in anhydrous condition from the second effect and can be recycled to feed blending Without further treatment `after being condensed in the first effect boiler 36 and preheater v28.

This combination of countercurrent heat exchange and anhydrous concentration under pressure effects a very great saving in the amount of refrigeration required for cooling of the feed and for the purification and fractional separation of the recycle material, and also eliminates the necessity of compressing gases and expensive .drying of recycle streams with chemical adsorbents. The purication operations are confined to the vapor stream leaving the flash drum, which is a small proportion -of the total stream recycled.

From the final evaporating drum, the fairly concentrated solution, preferably containing at least of polymer, and -better'containing from y20 to 25% of polymer, is delivered to a steam dispersion jet 46 by which it is converted to a condition substantially free from volatiles, and moistened by condensed ,steam or Water from other sources which maintains the dispersed condition. The lje't of steam and circulating water carry the moistened solid polymer particles into a pool of hot water in the ash drum, with most of the solvent and traces of unpolymerized unsaturates removed. The residual solvent from the flash drum is, 4of course, contaminated with substantial quantities of water vapor from the hot water, and. accordingly, it is not directly usable in the recycle system. However, by condensation of the vapor output from the ilash drum, a simple separation of most of the water in a settling tank is possible, thereby greatly reducing the diiculty of purication, and the very low tend,-V ency of the Vhydrocarbon to form hydrates permits of a .final ,purification by distillation alone, after which the hydrocarbon material may be tractionated to recover separately the butane, isobutylene and risoprene in pure form, suitable 4for -re-blending and recycling.

lIntheflash drum 44, the broken up stream of polymer drops into the water in the form of a stable slurry in water whichis discharged from the 4bottom of therflash' tank-from which-itis `conveyed to a slurry stripper for stillfurther removalof volatiles andthendeliveredunder pump pressure through pipes to .a strainer as above outlined, lwhich may be `an Oliver type -filter 'or maybe Ia vibrating screen filter, .or maybe a traveling yscreen filter, or other pattern as desired. This .screening lstep brings the water content down .to 50% or below. The screened polymer :may then be delivered to Aa steam-.heated tunnel dryer lin which the watercontent mayibe brought to .1% or below, after which the .polymer may be treated yon the double roll mill, or in anextruder to bring the Water content to values below .0.5

By `this process 'and Lapparatus of the inVention,-it is possible lto `polymerize vand copolymerize isoolelnsand. multiolens at .temperatures from 0 C. down to 164 C., preferably within the .range between 40 C. .or `3S C., and 103 C., by the use of only sufficient refrigeration to absorb the heat -of reaction `and fthe amount of heat represented :by the specific `heat ofthe polymerizate mixture multiplied 4by the temperature gradient -in the heat-exchanger walls, this Vbeing a relatively smal'l fraction of the total yheat required-.to cool the material and absorb the Yheat `.of reaction.

Thus, the process olf the .invention mixes together an olelinic material .in relatively small volume with a considerably :greater volume of .solvent which may conveniently be `but'ane, cools the mixture by countercurrentow through iheat exchangers from va Acold polymerizate overflow, and delivers the cold mixture to a polymerizer-cir-` culating system in which the cold olefin-solvent `mixture is yfurther cooled by heat exchangers jacketed with -a refrigerant liquid, a catalyst injection v.means and a reaction drum;` the heat exchangers serving `alternately as nal [feed coolers and `polymerization mixture coolers, from which system the .polymer solution .overow, lafter passage through thevcountercurrentvheat exchangers is further heated to vaporize out a major portion of the-.solvent, to leave a hot, more concentrated solution, which is then vigorously mixed with steam and lhot Water to convert the solutionof polymer in solvent, into a slurry of polymer in Water from which the polyer -is strained and dried, `the rst evaporated portion of solvent being evaporated under anhydrous conditions so as to be direct'ly usable for recycle, the second portion of .solvent evaporated by the steam being condensed, separated Vfrom the water, fractionally distilled to remove undesired residues, and acceptable portions then recycled.

The Aprocedure of the invention and 4the apparatus outlined above is Vparticularly adapted to the use of butane as solvent diluent for the polymerization reaction. As an alternative, a higher boiling solvent such as isopentane may be used, especially when butadiene is the multiolen. For this purpose a substantially identical heat 'interchange cooling system may be Vused as shown in Fig. 2. In this system there is shown the .cooled system, consisting of feed input `pipe -1, .heat interchangers "2, 3, 4, 5 and 6, which may be used with a calcium chloride dryer 7 if desired, discharging through a cold feed pipe 8 to a similar circulating polymerizer `system T9, including ethylene coolers 11 and 1'2, alternately connected -by pipes 14 and 15 through a vcirculating pipe 16 and catalyst injection nozzle 17 to an input pipe 18 and to a `polymerizer drum I9 and circulating pump '21 closely similar to the system shown in Fig. l. As is Well shown in Fig. V2, a similar over'ow is taken through the pump 25 and drum 26y through the :heat exchange members 6, 5, 4, 3 and 2 to the discharge pipeV 27 whichf'is led to the preheater 2S, boiler 36, andboiler drum 29. A modification may be intro- 13 duced at `this point, the pipeline 31 for volatilized material being led through the preheater 28 and then to a condenser member 131 and pomp 132.

With pentane, either iso or normal, las the solventdiluent, most of the methyl chloride from the catalyst solution, most of the isobutylene and most of the butadiene, when such is used, leave the polymer solution in the drum 29, about 3A of the diluent also being evaporated. This mixture is discharged through the pipe 133 to the fractionating tower 134, from which the bottoms go directly to recycle feed blending, and overhead is substantially pure methyl chloride suitable for preparation of catalyst solution. From the bottom of drum 29, the thickened polymer solution is delivered by a pump 37 and pipe 43 to `a jet 45 positioned within a receiver line 46 connected to a flash tank 44. A steam line 47 is connected to a jet associated with the polymer solution jet 45, and also a tangential jet of water, either fresh or recirculated from the tank 44, as desired, which together break up the polymer solution into relatively tine particles ,and lpermits of rapid disengagement of residual volatiles from the solid polymer and at the same time converts the solution into a slurry of polymer in water, which is transferred to a strainer to bring the water content to about 50% and then through a tunnel dryer to bring the Water to a lower value preparatory to milling. The residual pentane and unsaturates containing traces of methyl chloride `is taken overhead from the drum 44 to a condenser 48. The residual pentane unsaturates, methyl chloride, and the moisture carried over from tank 44 are condensed and delivered to a separator 49, where the water settles to the bottom and is drained away through a drain 51 and the condensed pentane is delivered into a pipe 52 to a pump 53, by which itis discharged through a line 54 to a fractionating tower 55, from which residual traces of water are discharged overhead through a pipe 56 |and the bottoms are carried through a pipe 57 :to a second tower 58 from which residual methyl chloride is taken overhead and the bottoms are carried through a pipe 67 to a third fractionating tower 68, the bottoms from which are taken to `a fourth fractionating tower 169, from which the pentane is taken overhead for recycle and bottoms are sent to waste. The overhead from the third tower 68 is sent to a fth tower 171. This fifth tower recovers butadiene from the C4 purge stream by an extractive distillation with acetone. Alternatively, other recovery methods may be used such as extraction with a copper salt solution and the like. From this tower 171 the bottoms are taken through a line 172 to `a sixth tower 173, the bottoms from which, consisting of acetone and water, are returned to the tower 171 for reux and the tops are taken to a butadiene washing tower 174, the overhead of which is a good grade of butadiene which is sent directly to the recycle mixing equipment; the bottoms which consist of water and impurities `are sent to waste. The overhead from the tower 171 contains C4 impurities and is purged.

The differences in Figures l and 2 indicate approximately the differences in process steps and in apparatus necessary for adjustment of the system to the use of various types of polymerizate materials `and different solvents.

The process yand system of the present invention is particularly desirable for some of the more diicult polymerizations. The prior commercially successful polymerization produced a copolymer of isobutylene and isoprene between which the copolymerizability ratio is close to unity and a mixture of 95 to 98 parts of isobutylene with from 5 to 2 parts `of isoprene yields a copolymer containing isoprene copolymerized into the copolymer molecule in the proportion `of from 1 to 2.5 or 3 molecular percent. This material makes an excellent replacement for rubber, especially for automobile inner-tubes as well as for proofed goods, and many other uses.

iIt is found that the poisoning effect of isoprene, o1' impurities introduced with isoprene, upon the reaction Iis great enough so that when more than about 10, l2 or 15% of isoprene is present, `difficulty is encountered in obtaining a sufficiently high molecular weight. In contrast, the poisoning effect of butadiene upon the reaction is much lower, but the `copolymerizability ratio is much poorer. Hence, when it is desired to produce polymers containing from 3 to 5 molecular percent of the multiolefin, with butadiene, there must ybe present from 30% to 75% of butadiene y(the remainder being isobutylene), the mixture of unsaturates then being diluted with a substantial portieri of diluent. However, when butadiene is used as the multioletin, the rel-atively high proportion of butadiene necessarily present gives a solvating effect to the polymer when in methyl chloride slurry, which introduces extreme difliculty in getting the polymer out of the polymerizer, since it coalesces into very large chunks and largely adheres to the polymerizer walls. Accordingly, to the present, it has been commercially unfeasible to operate `a `continuous polymerizer on butadiene as the multiolefiin because of the many and very great manufacturing diculties. However, the present process overcomes those difficulties and since the polymer remains -at all times in solution, no fouling problems are encountered.

By this procedure lit thus becomes possible to produce polymers `of isobutylene and butadiene in which the copolymerized butadiene may be present in proportions from l0 to 50 molecular percent with the correspondingly increased iodine number up to 175 as is well shown by the copending application of Nelson and Welch, Serial No. 788,640, filed November 28, 1947, now Patent No. 2,607,764 (which is herewith made part of the present application).

Similarly, this procedure overcomes most of the manufacturing diliiculties encountered in the preparation of other copolymers of 4isobutylene with a wide range of multiolens as above outlined.

Also, the process and apparatus are particularly well adapted to the manufacture of the hard resin prepared from a major proportion of butadiene and a minor proportion of a less easily copolymerizable monoolen such as with iso-octene, known as dimer (prepared by the dimerization of isobutylene) as is particularly well shown in Serial No. 604,350, filed July 17, 1945, now abandoned and Serial No. 610,212, filed August l0, 1945, now Patent No. 2,476,000 (both of which are herewith made parts of the present application).

ln general the process and apparatus here disclosed are used for the manufacture of any low temperature polymer which can be made in solution, to avoid fouling of reactor and to Iavoid loss of refrigeration with the incidental costliness of power and materials.

Thus the process of the invention copolymerizes unsaturates at low temperatures by the application of Friedel-Crafts catalyst thereto at low temperature in the presence of a solvent for the unsaturates and for the completed polymer, utilizing the refrigeration in the cold polymer solution to cool incoming monomer-solvent feed, absorbs the heat of reaction by direct refrigeration in a circulating polymer solution system, utilizing sufficient amounts of solvent during the polymerization to keep the solution viscosity within a tlowable range of values at the low temperature, then warming up the solution to conserve refrigeration and reduce viscosity of the solution simultaneously, vaporizing out a major portion of the solvent at elevated temperature, well above polymerization temperature to recover directly, and under anhydrous conditions a recycle stock, relying upon the higher temperature to maintain the viscosity of the concentrated polymer solution within owable range, then simultaneously steam vaporizing the residual volatiles, and water slurrying the dissolved polymer in solid form in the water for recovery, drying the residual unsaturates by condensation, settling, mechanical separation, nishing the drying by fractional distillation, then fractionally separating the several components of the steam-vaporized volatiles for reblending and recycling.

y While there are above disclosed but a limited number of Aembodiments of the process and apparatus of the invention, it is possible to produce still other embodiments without departing from the inventive concept herein disclosed, and it is therefore desired that only such limitations be imposed upon the appended claims as are stated therein or required by the prior art.

What is claimed is:

l. In a polymerization process for manufacturing an isobutylene-diolen synthetic rubber, the steps in combination of circulating a cold mixture of polymerizable unsaturated reactants comprising a maior proportion of isobutylene and a minor proportion of a multioletin of 4 to 14 carbon atoms and 3 to 25 volumes, per volume of reactants, of a C3 to C8 saturated hydrocarbon solvent for both the unsaturates and polymer, having a boiling point within the range of 40 C. to +69 C., at appolymerization temperature of about 40 C. to 103 'C ,fadding thereto during circulation suicient Friedel-Crafts lactive metal halide polymerization catalyst dissolved in `a low-freezing non-complex forming solvent, ytoeffe'ct substantial polymerization of the reactants but not more than required to produce a pumpable dilute polymer :solution of not over 5% concentration having a viscosity'within a flowable range and having Vgood heat transferand-catalyst dispersion, withdrawing from the circulating l'system as a continuing stream a portion of said colddilutepolymer solution, replacing the withdrawnpolymer solution by 'a steady stream of fresh feed of `mixed unsaturated reactants and solvent, cooling said fresh vfeed first .by countercurrent heat-exchange with the Withdrawnstream of cold dilute polymer solution to cool said feed toatemperature close to polymerization temperature, and `to warm the withdrawn cold dilute polymer ysolution nearly to the temperature of the incoming feed, and iinally .cooling said feed, prior to feeding it into the circulatingY polymerizaticn system, to the desired polymerization temperature by heat-exchange with a liquid cooling mediumwhich boils at the desired polymerization temperature heating the withdrawn dilute polymer solution further tothe :boiling point of the solvent therein and continuing the heating to evaporate a major proportion of said solvent and unreacted reactants till a hot concentrated still-owable polymer solution of -35% polymer is obtained,;and finally discharging the hot concentrated polymer solution into hot water to evaporate remaining solvent :and reactants and to make a slurry of .polymer and water, and recovering and recycling evaporated solventandreactan'ts as fresh feed.

2. Process according to claim l, using isoprene as the multiolefin, and butano as solvent.

3. vProcess according to `claim l, using isoprene as'the multioleiin, and an .alkane of 6 -to `3 carbon atoms `,as solvent.

4. Process according to claim l, using butadiene as the multiolen, and pentane as solvent.

5. Process according to claim l, `using butadiene `as multiolefin, and an alkane of 6 yto `8 carbon vatoms as solvent.

6. In a vpolymerization process for manufacturing :an isobutylene-diolen synthetic rubber, the steps in 4combination 'of circulating a-`cold mixture of polymerizable'unsaturated reactantsfcomprising a major proportion of isobutylene and a minor .proportion of a dioletin of `4 :to 6

carbon 'atoms and 3 to '25 volumes, per volume fo'f reactants, of a C4 tovCq saturated'hydrocarbon solvent for both the .unsaturates rand polymer, at a polymerization temperature of aboutl 95 C. to 103 C., addingthereto during circulation suicientFriedel-Crafts active metalr halide polymerization catalyst,=`clissolved 'in alow-freezing,

non-'complex forming solvent, to effect substantial polymerization of the reactants `but :not more than 'required to'produce apumpable dilute polymer solution of not over 16 5% concentration having a viscosity within a flowable range and having good heat transfer and catalyst dispersion, withdrawing from the circulating system as a continuingstream a portion of said cold, dilute polymer solution, replacing the withdrawn solution by a steady stream l of-'fresh feed of mixed unsaturatedA reactants and solvent,

cooling said fresh feed rst by countercurrent heat-exchange, in a series of heat-exchange zones, with the withdrawn stream of cold dilute polymer solution to cool said feed to a temperature close to the desired polymerization temperature, and to warm the Withdrawn coldV dilute polymer solution nearly to the temperature of the incoming feed, and'nally, cooling said feed, prior to feeding it into thecirculating polymerization system, -to the desired polymerization temperature by 'heat-exchange with liquid ethylene, in a vsystem of at least two cooling zones `connected in parallel with valve controls to permit alternately the use fof one for cooling'the circulating mixture, while theother is used for final cooling of incoming fresh feed, and 'periodically reversing these cooling surfaces whenthe ethylene cooler used for cooling circulating polymerization mixturebecomes fouled by deposition of a layer-of polymer on the cooling surfaces, heatingthe withdrawn dilute polymer solution further to the boiling-point of the solvent :therein and continuing with the heating to evaporate a major proportion of said solvent and unreacted reactants till -a hot concentrated still-flowable polymer solution of l5-25% polymer is obtained, and finally discharging the -hot concentrated polymer solution into hot water to evaporate remaining solvent and reactantsand to make a slurry and water, and recovering and recycling evaporated solventl and reactants as fresh feed.

v7. In Iapol-ymerization process for manufacturing an isobutylene-diolen synthetic rubber, the -steps in combination `of circulating a cold mixture of polymerizable unsaturated `reactants comprising a major proportion of isobutylene and a vminor proportion of ya multiolen of 4 to 14 1carbon Vatoms and 3 to 25 volumes, per vvolume of reactants,- of a C3 to C3 saturated hydrocarbon solvent' for both the unsaturates and polymer, having a boilingipoint within the range of 40 C. to +69 C., at 'apolymerizationtemperature of about 40 C. to 103 C., adding thereto during circulation sutiicient Friedel-'Crafts active metal halide polymerization catalyst dissolved inta low-.freezing non-.complex forming solvent, to ,eifect'subvstant'ial `polymerization .of the reactants4 but not `more than required to produce a pumpable dilute ypolymer solution of not over 5% concentration having 'a viscosity within a flowable range and having 'good heat-transfer and catalyst dispersion, withdrawing from the'ci'rculating system :as a continuing'stream aportion ofsaid cold'dilute polymer solution, replacing `the withdrawn polymersolution by `a steady stream of fresh feed of mixed vunsaturated react-ants and solvent, cooling said vfresh feed first 'by countercurre'nt heat-exchange with the withdrawn lstream of cold dilute .polymer `solution to cool said feed to a temperature close to polymerization temperature, and to warm the withdrawn cold dilute polymer solution lnearly to the temperature of the incoming feed, and finally cooling said feed, prior to feeding it into the circulating polymerization system, to the desired polymerization temperature by heat-exchange with Aa liquid cooling medium Awhich boils at the desired polymerization temperature.

8. Process as defined by claim 7 wherein said polymerzation-cat-alyst comprises aluminum bromide.

' 9. Process as `defined lby claim 8 wherein said saturated hydrocarbon solvent is selected from the group of saturated hydrocarbon `solvents having 6 to 7 carbon atomsinthe molecule.

l0. Process :as deiined by claim 8 wherein said low freezing non-complex forming solvent is selectedfrom the .classv ofsaturated `hydrocarbon solvents having 6 to 7 carbony atoms inthe molecule.

11. Process as defined by claim wherein said multioleiin comprises isoprene.

12. Process as defined by claim 11 wherein the concentration of the polymer in the dilute solution is in the range from about 1% to 3%.

13. In a polymerization process for manufacturing an isobutylene-diolen synthetic rubber having a Staudinger molecular weight of about 35,000 to 60,000, the steps in combination of circulating a cold mixture of polymerizable unsaturated reactants comprising a major proportion of isobutylene and a minor proportion of a diolein of 4 to 6 carbon atoms and 3 to 25 volumes, per volume of reactants, of a C4 to C7 saturated hydrocarbon solvent for both the unsaturates and polymer, at a polymerization temperature of about 40 C. to 103 C., adding thereto during circulation sufficient Friedel-Crafts active metal halide polymerization catalyst, dissolved in a lowfreezing, non-complex forming solvent, to effect substantial polymerization of the reactants but not more than required to produce a pumpable dilute polymer solution of not over 5% concentration having a viscosity within a flowable range and having good heat transfer and catalyst dispersion, withdrawing from the circulating system as a continuing stream a portion of said cold, dilute polymer solution, replacing the withdrawn solution by a steady stream of fresh feed of mixed unsaturated reactants and solvent, cooling said fresh feed first by countercurrent heat-exchange, in a series of heat-exchange zones, with the withdrawn stream of cold dilute polymer solution to cool said feed to a temperature close to the desired polymerization temperature, and to warm the withdrawn cold dilute polymer solution nearly to the temperature of the incoming feed, and iinally, cooling said feed, prior to feeding it into the circulating polymerization system, to the desired polymerization temperature by heat-exchange with refrigerant, in a system of at least two cooling zones connected in parallel with valve controls to permit alternately the use of one for cooling the circulating mixture, while the other is used for final cooling of incoming fresh feed, and periodically reversing these cooling surfaces when the cooler used for cooling circulating polymerization mixture becomes fouled by deposition of a layer of polymer on the cooling surfaces.

14. In a polymerization process for manufacturing au isobutylene-diolen synthetic rubber having a Staudinger molecular weight of about 35,000 to 60,000, the steps in combination of circulating a cold mixture of polymerizable unsaturated reactants comprising a major proportion of isobutylene and a minor proportion of a dioleiin of 4 to 6 carbon atoms and 3 to 25 volumes, per volume of reactants, of a C6 to C7 saturated hydrocarbon solvent for both the unsaturates and polymer, `at a polymerization temperature of about 40 C. to 103 C., adding thereto during circulation suicient Friedel-Crafts active metal halide polymerization catalyst, dissolved in a low-freezing, non-complex forming solvent, to effect substantial polymerization of the reactants but not more than required to produce a pumpable dilute polymer solution of not over 5% concentration having a viscosity within a iiowable range and having good heat transfer and catalyst dispersion, withdrawing from the circulating system as a continuing stream a portion of said cold, dilute polymer solution, replacing the withdrawn solution by a steady stream of fresh feed of mixed Iunsaturated reactants and solvent, cooling said fresh feed iirst by `countercurrent heat-exchange, in a series of heat-exchange zones, with the withdrawn stream of cold dilute polymer solution to cool said feed to a temperature close to the desired polymerization temperature, and to warm the withdrawn cold dilute polymer solution nearly to the temperature of the incoming feed, and finally, cooling said feed, prior to feeding it into the circulating polymerization system, to the desired polymerization temperature by heat-exchange with refrigerant, in a system of at least two cooling zones connected in parallel with valve controls to permit alternately the use of one for cooling the circulating mixture, while the other is used for final cooling of incoming fresh feed, and periodically reversing these cooling surfaces when the cooler used for cooling circulating polymerization mixture becomes fouled by deposition of a layer of polymer on the cooling surfaces.

15. Process as defined by claim 14 wherein said metal halide polymerization catalyst comprises aluminum bromide.

16. Process as defined by claim 15 wherein said lowfreezing non-complex forming solvent is selected from the class of saturated hydrocarbons having 6 to 7 carbon atoms in the molecule.

17. Process as defined by claim 16 wherein the concentration of polymer in the dilute solution is in the range from about l to 3%.

18. Process as defined by claim 16 wherein said dioleiin comprises isoprene.

19. In a polymerization process for manufacturing an isobutylene-dioleiin synthetic rubber having a Staudinger molecular weight of about 35,000 to 60,000, the steps in combination of circulating a cold mixture of polymeriz-able unsaturated reactants comprising a major proportion of isobutylene and a minor proportion of a dioleiin of 4 to 6 carbon atoms and 3 to 25 Volumes, per volume of reactants, of a C4 to C, saturated hydrocarbon solvent for both the unsaturates and polymer, at a polymerization temperature of about 40 C. to 103 C., adding thereto during circulation 'sufficient Friedel-Crafts active metal halide polymerization catalyst, dissolved in a lowfreezing, non-complex forming solvent, to effect substantial polymerization of the reactants but not more than required to produce a pumpable dilute polymer ysolution of not over 5% concentration having a viscosity within a flowable range and having good heat transfer and catalyst dispersion, withdrawing from the circulating system as Ia Icontinuing stream a portion of said cold, dilute polymer solution, replacing the withdrawn solution by a steady stream of fresh feed of mixed unsaturated reactants and solvent, cooling said fresh feed first by countercurrent heat-exchange, in a series of heat-exchange zones, with the withdrawn stream of cold dilute polymer solution to cool said feed to a temperature close to the desired polymerization temperature, and to warm the withdrawn cold dilute polymer solution nearly to the temperature of the incoming feed, and finally, cooling said feed, prior to feeding itinto the circulating polymerization systern, to the desired polymerization temperature by heatexchange with refrigerant, in a system of at least two cooling zones connected in parallel with valve controls to permit Ialternately the use of one for cooling the circulating mixture, while the other is used for nal cooling of incoming fresh feed, and periodically reversing these cooling surfaces when the ethylene cooler used for cooling circulating polymerization mixture becomes fouled by deposition of a layer of polymer on the cooling surfaces, heating the withdrawn dilute polymer solution further to the boiling point of the solvent therein and continuing with the heating to evaporate a ma'jor proportion of said solvent and unreacted reactants till a hot concentrated still-flowable polymer solution of 15-25% polymer is obtained, and finally discharging the hot concentrated polymer solution into hot water to evaporate remaining solvent and reactants and to make a slurry and water, and recovering and recycling evaporated solvent and reactants as fresh feed.

References Cited in the tile of this patent UNITED STATES PATENTS 2,583,420 Garber et al Jan. 20, 1952 

1. IN A POLYMERIZATION PROCESS FOR MANUFACTURING AN ISOBUTYLENE-DIOLEFIN SYNTHETIC RUBBER, THE STEPS IN COMBINATION OF CIRCULATING A COLD MIXTURE OF POLYMERIZABLE UNSATURATED REACTANTS COMPRISING A MAJOR PROPORTION OF ISOBUTYLENE AND A MINOR PROPORTION OF A MULTIOLEFIN OF 4 TO 14 CARBON ATOMS AND 3 TO 25 VOLUMES, PER VOLUME OF REACTANTS, OF A C3 TO C8 SATURATED HYDROCARBON SOLVENT FOR BOTH THE UNSATURATES AND POLYMER, HAVING A BOILING POINT WITHIN THE RANGE OF -40*C. TO +69*C., AT A POLYMERIZATION TEMPERATURE OF ABOUT -40*C. TO -103*C., ADDING THERETO DURING CIRCULATION SUFFICIENT FRIEDEL-CRAFTS ACTIVE METAL HALIDE POLYMERIZATION CATALYST DISSOLVED IN A LOW-FREEZING NON-COMPLEX FORMING SOLVENT, TO EFFECT SUBSTANTIAL POLYMERIZATION OF THE REACTANTS BUT NOT MORE THAN REQUIRED TO PRODUCE A PUMPABLE DILUTE POLYMER SOLUTION OF NOT OVER 5% CONCENTRATION HAVING A VISCOSITY WITHIN A FLOWABLE RANGE AND HAVING GOOD HEAT TRANSFER AND CATALYST DISPERSION, WITHDRAWING FROM THE CIRCULATING SYSTEM AS A CONTINUING STREAM A PORTION OF SAID COLD DILUTE POLYMER SOLUTION, REPLACING THE WITHDRAWN POLYMER SOLUTION BY A STEADY STREAM OF FRESH FEED OF MIXED UNSATURATED REACTANTS AND SOLVENT, COOLING SAID FRESH FEED FIRST BY COUNTERCURRENT HEAT-EXCHANGE WITH THE WITHDRAWN STREAM OF COLD DILUTE POLYMER SOLUTION TO COOL SAID FEED TO A TEMPERATURE CLOSE TO POLYMERIZATION TEMPERATURE, AND TO WARM THE WITHDRAWN COLD DILUTE POLYMER SOLUTION NEARLY TO THE TEMPERATURE OF THE INCOMING FEED, AND FINALLY COOLING SAID FEED, PRIOR TO FEEDING IT INTO THE CIRCULATING POLYMERIZATION SYSTEM, TO THE DESIRED POLYMERIZATION TEMPERATURE BY HEAT-EXCHANGE WITH A LIQUID COOLING MEDIUM WHICH BOILS AT THE DESIRED POLYMERIZATION TEMPERATURE HEATING THE WITHDRAWN DILUTE POLYMER SOLUTION FURTHER TO THE BOILING POINT OF THE SOLVENT THEREIN AND CONTINUING THE HEATING TO EVAPORATE A MAJOR PROPORTION OF SAID SOLVENT AND UNREACTED REACTANTS TILL A HOT CONCENTRATED STILL-FLOWABLE POLYMER SOLUTION OF 10-35% POLYMER IS OBTAINED, AND FINALLY DISCHARGING THE HOT CONCENTRATED POLYMER SOLUTION INTO HOT WATER TO EVAPORATE REMAINING SOLVENT AND REACTANTS AND TO MAKE A SLURRY OF POLYMER AND WATER, AND RECOVERING AND RECYCLING EVAPORATED SOLVENT AND REACTANTS AS FRESH FEED. 